Earth’s Structure

Layers of the Earth
- Crust: Composition, continental vs. oceanic
- Mantle: Structure, composition, convection currents
- Core: Inner and outer core, composition, geodynamo

The Earth’s interior, Source: Philpotts and Ague (2022)

Plate Tectonics

• Type of tectonics boundaries
• Formation of rock types

The layers of the tectonic Earth, (Source: Philpotts and Ague (2022))

Magma Generation and Plate Tectonics

Generalized cross section illustrating magma generation associated with various plate tectonic settings. Source: Winter, J. (2014)

Magma Generation

Processes of Melting

• Decompression melting
  Pressure decrease lowers the melting point of mantle rocks.
  Tectonic settings: mid-ocean ridges, mantle plumes → basaltic magma

• Flux melting (addition of water)
  Water released from a subducting slab lowers the mantle solidus.
  Tectonic settings: subduction zones → andesitic magma

• Heating of crust
  Basaltic magma underplates the continental crust and transfers heat.
  Tectonic settings: continental crust → granitic magma

• Partial melting
  Melting begins at mineral grain junctions; most magmas are mixtures of melt and crystals.
  Result: porphyritic textures common in igneous rocks

Sources of Magma

• Basalts → partial melting of mantle peridotite (olivine + pyroxene)
  
• Andesites → water-fluxed mantle wedge above subduction zones
  
• Granites → partial melting of continental crust

The Convergent Plate Boundary

The convergent plate boundary (Source: Jain, S. (2014))

The Ocean–Ocean Convergence

The Ocean–Ocean convergence (Source: Jain, S. (2014))

The Ocean–Continent Collision

The Ocean–Continent collision (Source: Jain, S. (2014))

Divergent Plate Boundary

The Divergent Plate Boundary (Source: Jain, S. (2014))

Example of Divergent Plate Boundary

The East Africa Rift Valley and the Red Sea rift (Source: Jain, S. (2014))

Hot Spots and Mantle Plumes

Schematic model for oceanic volcanism. Source: Winter, J. (2014)